Drive mechanism for a vehicle access system

ABSTRACT

An access system for passenger boarding of a vehicle is provided. The access system includes a frame mounted to the vehicle. A transfer member is movably mounted in the frame. The transfer member is movable with respect to the frame between a stowed position and a deployed position with respect to the vehicle. A first drive assembly is positioned along a first side of the frame and a second drive assembly is positioned along a second side of the frame. A linking member extends between and connects the first drive assembly with the second drive assembly. There is further provided a control assembly that is engageable to at least one of the linking member, the first drive assembly, and the second drive assembly to allow operator selection of a manual or automatic mode for deploying and stowing the transfer member.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date ofProvisional Application No. 60/264,279, filed Jan. 26, 2001.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the field of vehicleaccess systems, and more particularly to drive mechanisms for deployingand stowing a transfer member of a vehicle access system.

[0003] There are many types of drive mechanisms known to deploy and stowramps, lift platforms and other transfer members that provide wheelchairaccess to vehicles. One type of drive mechanism is described in U.S.Pat. No. 6,102,648 to Fretwell et al. Another example is provided inU.S. Pat. No. 5,393,192 to Hall et al.

[0004] While various drive mechanisms for extending and retractingtransfer members from vehicles are known, there remains a need forimprovements in the art. For example, there remains a need for improvedvehicle access systems that deploy and stow the transfer member whilealso maintaining its alignment. There also remains a need for vehicleaccess systems that allow a transfer member to be manually stowed whilemaintaining alignment of the transfer member within its frame.Furthermore, there is a need for vehicle access systems that employmultiple drive assemblies for deploying and stowing a transfer member inboth automatic and manual modes. The present invention is directedtowards meeting these needs, among others.

SUMMARY OF THE INVENTION

[0005] One aspect of the present invention is directed to a vehicleaccess system which includes a transfer member that provides wheelchairaccess to a vehicle. The transfer member is coupled to a pair of driveassemblies that are interconnected by a linking member and provide aconcentric driving force to move the transfer member between its stowedand deployed positions.

[0006] In one form, the interconnected drive assemblies are maintainedsimultaneously in either an automatic mode or a manual mode to deploy orstow the transfer member. In a further form, a locking member isprovided that allows operator selection of the automatic mode or themanual mode. The locking member can be selectively engageable to one ofthe drive assemblies and the linking member in order to select thedriving mode desired.

[0007] In another aspect of the present invention, a vehicle accesssystem is provided. The access system includes a frame having oppositefirst and second sides extending between an inboard end and an outboardend. A transfer member having an inboard end and an outboard end ismovably supported by the frame. The system further includes a firstdrive assembly positioned adjacent the first side of the frame and asecond drive assembly positioned adjacent the second side of the frame.A linking member extends between and connects the first drive assemblywith the second drive assembly. A control assembly is selectivelyengageable to at least one of the linking member, the first driveassembly, and the second drive assembly. The first drive assembly andthe second drive assembly are operable to move the transfer member withrespect to the frame between a stowed position whereby the transfermember is positioned substantially in the vehicle, and an deployedposition whereby the transfer member extends outwardly from the vehicle.

[0008] In a further aspect of the present invention, the first andsecond drive assemblies each include a chain mounted to the frame and amotor coupled to the chain The chains are fixed and the motors aremovable along their respective chain when the locking member is engaged.The linking member includes a chain extending between and connecting thefirst drive assembly to the second drive assembly. A first doublesprocket connects the first chain of the first drive assembly to thechain of the linking member, and a second double sprocket connects thesecond chain of the second drive assembly to the chain of the linkingmember. The control assembly can include a locking member that isselectively engageable to one the first and second double sprockets. Thetransfer member can be manually moved between the extended and retractedposition when the control assembly is disengaged.

[0009] In another aspect of the present invention, the access systemincludes a carriage attached to the inboard end of the transfer memberthat is movable in the frame. The first drive assembly and the seconddrive assembly include a first motor and a second motor, respectively,mounted in the carriage. The first drive assembly includes a first chainmounted to the frame with the first motor coupled thereto. The firstchain is fixed and the first motor is movable along the first chain whenthe locking member is engaged. The second drive assembly includes asecond chain mounted to the frame with the second motor coupled thereto.The second chain is fixed and the second motor is movable along thesecond chain when the locking member is engaged.

[0010] In one form, the access system includes means for raising theinboard end of the transfer member. The access system includes acarriage movable in the frame that is attached to the inboard end of thetransfer member. The means for raising includes a rocker assemblypivotally attached to and extending between an outboard end of thecarriage and the inboard end of the transfer member.

[0011] In another aspect of the present invention, a vehicle accesssystem is provided. The system includes a frame having opposite firstand second sides extending between an inboard end and an outboard end. Atransfer member having an inboard end and an outboard end is movablymounted to the frame. A first drive assembly is positioned towards thefirst side of the frame. The first drive assembly includes a first chainand a first motor coupled to the first chain. A second drive assembly ispositioned towards the second side of the frame. The second driveassembly includes a second chain and a second motor coupled to thesecond chain. A linking member extends between and connects the firstdrive assembly with the second drive assembly. The first drive assemblyand the second drive assembly are operable to move the transfer memberwith respect to the frame between a retracted position whereby thetransfer member is positioned substantially in the vehicle and anextended position whereby the transfer member extends outwardly from thevehicle.

[0012] In one form, the vehicle access system also includes a controlassembly selectively engageable to the linking assembly. When thecontrol assembly is disengaged, the transfer member is manually movablebetween the extended and retracted positions. In another preferred form,the first motor is movable along the first chain and the second motor ismovable along the second chain to move the transfer member between theextended and retracted positions when the locking member is engaged tothe linking assembly. In another form, the first chain and the secondchain form first and second loops, respectively, that are orientedparallel to the frame. In a further form, the linking member is a chainextending along the inboard end of said frame connecting the first driveassembly and the second drive assembly.

[0013] In a further aspect of the invention, an access system forpassenger boarding of a vehicle is provided. The system includes a framemounted to the vehicle. The frame includes opposite first and secondsides extending between an inboard end and an outboard end of the frame.A transfer member having an inboard end and outboard end is movablymounted to the frame. A first drive assembly is positioned towards thefirst side of the frame and a second drive assembly is positionedtowards the second side of the frame. A chain is provided along theinboard end of the frame extending between and connecting the firstdrive assembly with the second drive assembly. The transfer member ismovable with respect to the frame by the first and second driveassemblies between a retracted position whereby the transfer member ispositioned substantially in the vehicle and an extended position wherebythe transfer member extends outwardly from the vehicle.

[0014] In one form, the transfer member has a central axis extendingbetween its inboard end and its outboard end. The first drive assemblyand the second drive assembly are each spaced an equal distance from thecentral axis on opposite sides thereof. In another form, the first driveassembly includes a first chain mounted to the frame and a first motorcoupled to the first chain. The first chain is fixed and the first motoris movable along the first chain when the locking member is engaged, andthe second drive assembly includes a second chain mounted to the frameand a second motor coupled to the second chain. The second chain isfixed and the second motor is movable along the second chain when thelocking member is engaged. It is also contemplated that the accesssystem can include a first double sprocket that connects the first chainof the first drive assembly to the chain of the linking member, and asecond double sprocket that connects the second chain of the seconddrive assembly to the chain of the linking member.

[0015] In still another aspect of the present invention, an apparatusfor deploying and stowing a transfer member of a vehicle access systemis provided. The apparatus includes a first drive assembly having afirst chain forming a substantially horizontal loop about a firstplurality of sprockets and a first motor engaged thereto. The apparatusfurther includes a second drive assembly having a second chain forming asubstantially horizontal loop about a second plurality of sprockets anda second motor engaged thereto. A linking member interconnects the firstand second drive assemblies. A control assembly is selectivelyengageable to one of the first drive assembly, the second driveassembly, and the linking member. The first and second drive assembliesare operable to move the transfer member between a stowed positionwhereby the transfer member is positioned substantially in the frame anda deployed position whereby the transfer member extends outwardly fromthe frame. When the control assembly is engaged, the first and secondmotors move along the first and second chains respectively. When thecontrol assembly is disengaged, the first and second chains rotate aboutthe first and second plurality of sprockets respectively.

[0016] These and other aspects, forms, features, embodiments, objectsand advantages of the present invention will be apparent from thefollowing detailed description of the illustrated embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a bottom plan view of a vehicle access system accordingto the present invention with a ramp in a stowed position along with acontrol schematic for operation of the same.

[0018]FIG. 2 is a bottom plan view of the vehicle access system of FIG.1 with the ramp in a deployed position.

[0019]FIG. 3 is a side elevation view of the vehicle access system ofFIG. 1 with the ramp partially extended from the vehicle.

[0020]FIG. 4 is a side elevation view of the vehicle access system ofFIG. 1 with the ramp fully extended from the vehicle.

[0021]FIG. 5 is a side elevation view of the vehicle access system ofFIG. 1 with the ramp fully extended from the vehicle and the inboard endof the ramp raised to the floor of the vehicle.

[0022]FIG. 6 is an enlarged top plan view of the vehicle access systemof FIG. 1 with the ramp in the stowed position.

[0023]FIG. 7 is an enlarged bottom plan view of the vehicle accesssystem of FIG. 1 with the ramp removed and the drive assemblies locatedin the deployed position.

[0024]FIG. 8 is a perspective view of the frame of the vehicle accesssystem of FIG. 1 with the ramp, carriage and drive assemblies removedtherefrom.

[0025]FIG. 9 is a sectional view taken through line 9-9 of FIG. 8.

[0026]FIG. 10 is an enlarged detailed perspective view of a portion of acontrol assembly of the vehicle access system of FIG. 1 with a portionof the frame cutaway. FIG. 11 is an enlarged top plan view of anothervehicular access system having a ramp and side barriers depicted withthe ramp and side barriers in a stowed low profile position in a frame.

[0027]FIG. 12 is a side elevation view of the vehicular access system ofFIG. 11 with the ramp partially extended from the vehicle and sidebarriers in the low profile orientation.

[0028]FIG. 13 is a side elevation view of the vehicular access system ofFIG. 11 with the ramp fully extended from the vehicle in a deployedposition and the side barriers in the low profile orientation.

[0029]FIG. 14 is a side elevation view of the vehicular access system ofFIG. 11 with the ramp in a vehicle floor level position and the sidebarriers in a raised safety barrier orientation.

[0030]FIG. 15 is a partial perspective view of the inboard end of theramp of the vehicular access system of FIG. 11 with the ramp in thedeployed position and one of the side barriers in the stowed orientationand the other side barrier removed.

[0031]FIG. 16 is a partial perspective view of the inboard end of theramp of the vehicular access system of FIG. 11 with the ramp in thevehicle floor level position and one of the side barriers in the raisedsafety barrier orientation and the other side barrier removed.

[0032]FIGS. 17a-17 d illustrate the orientation between the ramp,actuator, and the side barrier in, respectively, a stowed orientation, afirst partially pivoted side barrier position, a second partiallypivoted side barrier position, and a raised safety barrier orientation.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0033] For the purpose of promoting an understanding of the principlesof the invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended. Any alterations ormodifications of the illustrated devices or further applications of theprinciples of the invention illustrated herein that would occur to oneskilled in the art to which the invention relates are contemplated aswithin the scope of the invention.

[0034] Referring now to FIGS. 1-7, there is illustrated a vehicle accesssystem 10 according to the present invention. Vehicle access system 10includes a frame 12 having an inboard end 12 a and an outboard end 12 b.Frame 12 can be mounted to a vehicle V below the vehicle floor F (FIGS.3-5), below the frame, or in any other position that may occur to thoseskilled in the art. Outboard end 12 b preferably faces a direction fromwhich vehicle V is to be accessed. For example, outboard end 12 b mayface the side of a vehicle V (FIGS. 3-5.) Outboard end 12 b may alsoface any other position, such as, for example, the rear of a vehicle,such as would occur to one skilled in the art.

[0035] A transfer member is movably mounted to the frame 12 and is sizedto provide wheelchair access to the vehicle V from the ground G (FIGS.3-5.) In the illustrated embodiment, the transfer member is in the formof a ramp 20 that is moveably mounted within frame 12. While thetransfer member is illustrated and described herein with reference toramp 20, it should be understood that principles of the presentinvention also have application with other types of transfer members,such as, for example, a platform for a wheelchair lift. It shouldfurther be understood that the drawings of FIGS. 3-5 are not to scaleand that both ramp 20 and carriage 18 are sized to fit within frame 12in the stowed position.

[0036] Access system 10 includes a first drive assembly 14 and a seconddrive assembly 16 interconnected by a linking member 90 (see FIGS. 1, 2,6 and 7.) A control assembly 100 is provided to allow selection of theautomatic mode or the manual mode. Control assembly 100 is preferablyengaged to a portion of the first drive assembly 14 to select theautomatic mode of operation and disengaged from that portion to selectthe manual mode of operation. Linking member 90 connects first driveassembly 14 to second drive assembly 16, and control assembly 100 mayalternatively engage and disengage a portion of the linking member 90 ordrive assembly 16 to select the automatic and manual modes. In anyengaged configuration, linking member 90 maintains drive assemblies 14and 16 simultaneously in an automatic mode for deploying and stowingramp 20 using drive motors 52 and 72, respectively. When disengaged,linking member 90 maintains drive assemblies 14, 16 in a manual mode fordeploying and stowing the ramp 20 using manual force as may be required,for example, if power to drive motors 52 and 72 is interrupted.

[0037] Frame 12 has a first side rail 24 and a second side rail 26 inwhich wheels 28 of ramp 20 and wheels 30 of carriage 18 are mounted andmovable therealong. Ramp 20 has an inboard end 20 a and an oppositeoutboard end 20 b. Similarly, carriage 18 has an inboard end 18 a and anoutboard end 18 b. Inboard end 20 a of ramp 20 is hingedly attached tooutboard end 18 b of carriage 18 by a rocker assembly 32. Ramp 20 andcarriage 18 are movable within frame 12 between the stowed position(FIG. 1) and the deployed position, (FIG. 2) by first drive assembly 14and second drive assembly 16.

[0038] Drive motors 52 and 72 of drive assemblies 14 and 16 are poweredby a power source P (FIG. 1) which can be the power unit of the vehicleor a separate power unit. An operator can automatically stow and/ordeploy the ramp 20 by selecting deploy and stow switches S1 and S2 whichare operatively connected to control module 48. An emergency stop switchE is also operatively connected to control module 48 in order to stopautomatic deployment and/or stowing of ramp 20. The operative connectionfrom power unit P, deploy and stow switches S1 and S2 and control switchE to control module 48 can be accomplished through hardwiredconnections, radio frequency transmission or any other signaltransmission technique known in the art. Control module 48 is connectedto a power cable 46 which is electrically coupled to drive motor 52 offirst drive assembly 14, drive motor 72 of second drive assembly 16 andto lift motor 44 of lifting mechanism 37. Power cable 46 is preferablyflexible so it travels along with ramp 20 and carriage 30 withoutkinking or binding as they move inboard and outboard relative to frame12. Sensors (not shown) are preferably provided at or near inboard end12 a and outboard end 12 b of frame 12 in order to automatically stopmovement of ramp 20 when it is fully deployed or stowed and to sequenceoperation of drive assemblies 14 and 16 with lifting mechanism 37. Thesensors may be contact sensors, optical sensors, magnetic sensors or anyother sensors known in the art.

[0039] As best shown in FIGS. 6 and 7, rocker assembly 32 extendsbetween and is pivotally attached to inboard end 20 a of ramp 20 andoutboard end 18 b of carriage 18. Rocker assembly 32 includes firstrocker shaft 34 a rotatably connected to the outboard end 18 b ofcarriage 18 and second rocker shaft 34 b rotatably connected to theinboard end 20 a of ramp 20. Rocker shafts 34 a and 34 b areinterconnected by a number of struts 36 extending therebetween. Thelength of struts 36 is preferably adjustable to accommodate differingelevations between the floor F of vehicle V and frame 12. When ramp 20has been fully extended from the vehicle V, outboard end 20 b of ramp 20is on or near ground G, but inboard end 20 a of ramp 20 is below thelevel of floor F (FIG. 4.) From this position lifting mechanism 37 isoperable to rotate rocker assembly 32 about first rocker shaft 34 a tothereby raise inboard end 20 a of ramp 20 to the level of floor F ofvehicle V providing a smooth transition surface (FIG. 5.)

[0040] Referring now to FIGS. 4, 5, 6 and 7, further details of liftingmechanism 37 will be described. Lifting mechanism 37 includes abi-directional lift motor 44 mounted in carriage 18 and operable torotate a pinion 45 connected to the drive shaft (not shown) of motor 44.Pinion 45 is located below motor 44 and engages lift gear 42. Lift gear42 is rotatably mounted adjacent to the lower surface of carriage 18 andis driven in a clockwise or counterclockwise direction by motor 44 viapinion 45. Hub 43 is mounted concentrically to lift gear 42 and rotatestherewith. Lifting mechanism 37 further includes a lift arm 38 that ispivotally connected at one end to hub 43 at a location spaced away fromthe center of hub 43 and pivotally connected at its opposite end to ayoke 40 at one end of yoke 40. A spacer 39 provides a connection betweenyoke 40 and carriage 18 while permitting the rocking motion of yoke 40.Yoke 40 extends from its connection with lift arm 38 and spacer 39 to aconnector 35 that is attached to first rocker shaft 34 a.

[0041] The pivotal connections of lift arm 38 permit lift arm 38 totranslate the rotational motion of hub 43 in a plane of rotationsubstantially parallel to the bottom surface of carriage 18 to therocking motion of yoke 40 in a substantially perpendicular plane ofmotion. Connector 35 translates the rocking motion of yoke 40 into therotational motion of rocker shaft 34 a about its longitudinal axiswhich, in turn, raises inboard end 20 a of ramp 20 to the level of floorF of vehicle V as previously described.

[0042] When lift motor 44 is activated to raise inboard end 20 a of ramp20, pinion 45 drives lift gear 42 and rotates hub 43 in acounter-clockwise direction (FIG. 7.) This rotation moves lift arm 38towards inboard end 20 a of ramp 20. The motion of lift arm 38 rocksyoke 40 towards inboard end 20 a of ramp 20, thereby causing lowerrocker shaft 34 a to rotate about its own longitudinal axis at outboardend 18 b of carriage 18 and raise struts 36, upper rocker shaft 34 b,and inboard end 20 a of ramp 20 from their initial position (FIG. 4) tothe floor level F of vehicle V (FIG. 5.) Lift motor 44 is reversed tocause pinion 45 to drive lift gear 42 and rotate hub 43 in a clockwisedirection (FIG. 7.) This moves lift arm 38 away from inboard end 20 a oframp 20, rocks yoke 40 away from inboard end 20 a of ramp 20, andreturns inboard end 20 a of ramp 20 to its initial position (FIG. 4.)

[0043] The operation of drive assemblies 14 and 16 and linking member 90will now be further described. Side rails 24, 26 of frame 12 includeinwardly facing C-shaped portions 24 a and 26 a sized to received wheels28 of ramp 20 and wheels 30 of carriage 18. Carriage 18 and ramp 20 areconnected to one another by rocker assembly 32, and move together alongframe 12 in response to driving forces applied by first drive assembly14 and second drive assembly 16.

[0044] First drive assembly 14 includes a first bi-directional drivemotor 52 mounted in carriage 18 and moveable therewith between a stowedpositioned (FIG. 6) and a deployed position (FIG. 7.) First driveassembly 14 also includes a first drive chain 50. First drive motor 52includes a drive gear 64 that is operatively coupled to drive chain 50to apply a force thereto when motor 52 is powered on. A tension sprocket65 is rotatably mounted to carriage 18 and maintains chain 50 in contactwith drive gear 64. First outboard sprocket 60 is rotatably mounted toframe 12 adjacent outboard end 12 b. First inboard sprocket 54 and firstdouble sprocket 56 are each rotatably mounted to frame 12 adjacentinboard end 12 a. In the illustrated embodiment, double sprocket 56 ispositioned between side rail 24 and first inboard sprocket 54. Chain 50is looped around first outboard sprocket 60, first inboard sprocket 54,and lower cog 56 a of a first double wheeled sprocket 56. A tensionadjuster 58 is secured to first inboard sprocket 54 to maintain chain 50in a taut condition.

[0045] Second drive assembly 16 includes a second bi-directional drivemotor 72 mounted in carriage 18 and moveable therewith between a stowedposition (FIG. 6) and a deployed positions (FIG. 7.) Second driveassembly 16 also includes a second drive chain 70. Second drive motor 72includes drive gear 84 that is operatively coupled to second drive chain70 to apply a force thereto when motor 72 is powered on. Tensionsprocket 85 is rotatably mounted to carriage 18 and maintains chain 70in contact with drive gear 84. Second outboard sprocket 82 is rotatablymounted to frame 12 adjacent outboard end 12 b. Second inboard sprocket74, second double sprocket 76, and reversing sprocket 78 are rotatablymounted to frame 12 adjacent inboard end 12 a. In the illustratedembodiment, second double wheeled sprocket 76 is positioned betweensecond inboard sprocket 74 and reversing sprocket 78, and reversingsprocket 78 is positioned between second double wheeled sprocket 76 andside rail 26. A tension adjuster 80 is secured to second inboardsprocket 74 to maintain chain 70 in a taut condition.

[0046] Chain 70 is looped around second outboard sprocket 82, secondinboard sprocket 74, reversing sprocket 78 and second double wheeledsprocket 76. In order to permit manual deployment and stowing of ramp20, chain 70 extends around the outboard side of a lower cog 76 a ofsecond double wheeled sprocket 76 thereby permitting both double wheeledsprockets 56 and 76 to rotate in the same direction along with linkingmember 90 during manual deployment and stowing.

[0047] Linking member 90 interconnects first drive assembly 14 withsecond drive assembly 16. Linking member 90 is in the form of a loopchain which is connected around upper cog 56 b of first double sprocket56 and around upper cog 76 b of second double sprocket 76. Drive chain50 is connected around lower cog 56 a of double sprocket 56 and alsoaround first inboard sprocket 54 and first outboard sprocket 60, whichlie in generally the same horizontal plane as lower cog 56 a. Drivechain 70 is connected around lower cog 76 a of second double sprocket 76and also around second inboard sprocket 74, reversing sprocket 78, andsecond outboard sprocket 82, which lie in generally the same horizontalplane as lower cog 76 a. Although other orientations are contemplated,drive chains 50 and 70 and linking member 90 are oriented horizontallyin the illustrated embodiment to allow the overall height of frame 12 tobe reduced.

[0048] Referring now additionally to FIGS. 8-10, control assembly 100 isengageable to one of the first drive assembly 14, the second driveassembly 16, or linking member 90 to prevent movement of first drivechain 50, second drive chain 70, and linking member 90. In theillustrated embodiment, control assembly 100 includes a locking member102 secured to frame 12 at inboard end 12 a and movable with respectthereto. Locking member 102 is spring-biased into locking engagementwith a locking hub 62 provided on top of first double sprocket 56 by aspring 108. Spring 108 extends between and contacts abutment member 112at one end and slotted wall 114 of locking member 102 at the oppositeend. Locking member 102 is further coupled to a control cable 104.Control cable 104 is retained at one end in a cavity 115 of lockingmember 102 adjacent slotted wall 114. Control cable 104 extends throughslotted wall 114, spring 108, abutment member 112 and side rail 24. Asit exits side rail 24, cable 104 is surrounded by an outer sleeve 110and is coupled to a handle 106 at its opposite end. Handle 106 ispreferably positioned near outboard end 12 b of frame 12 for easy accessby the operator of access system 10.

[0049] Locking member 102 is released from locking hub 62 by pulling onhandle 106, thereby retracting cable 104 and locking member 102 in thedirection of arrow R (see FIG. 10), and compressing spring 108. Handle106 preferably includes a catch or the like that can be engaged byrotating handle 106 when locking member 102 is disengaged, allowinglocking member 102 to be maintained in the disengaged position formanual deployment and stowing of ramp 20.

[0050] When locking hub 62 is engaged by locking member 102 (see FIG.10) movement of first drive chain 50 prevented since first doublesprocket 56 is locked. Movement of second drive chain 70 is alsoprevented because linking member 90 interconnects second double sprocket76 with first double sprocket 56. This permits first drive motor 52 andsecond drive motor 72 to travel along fixed drive chain 50 and 70respectively when motors 52 and 72 are powered on. When locking member102 is disengaged from locking hub 62, however, drive chains 50 and 70and linking member 90 are free to rotate about their respective sprocketwheels. The relative movement of drive chains 50 and 70 is coordinatedby linking member 90 and allows manual movement of ramp 20 between thedeployed and stowed positions. Reversing sprocket 78 is provided toreverse the direction of movement of second double sprocket 76 relativeto second drive chain 70 when control assembly 100 is disengaged so thatdouble sprockets 56 and 76 rotate in the same direction while drivechains 50 and 70 rotate in opposite directions. Linking member 90 isthus free to rotate about double sprockets 56 and 76 when controlassembly 100 is disengaged allowing ramp 20 to be manually deployed andstowed within frame 12.

[0051] Access system 10 has a central axis A centrally positionedbetween side rails 24 and 26 of frame 12 and extending between inboardend 12 a and outboard end 12 b (FIGS. 6 and 7.) When control assembly100 is engaged, linking member 90 ensures that both drive chains 50, 70will not rotate so that each drive assembly 52 and 72 will move along afixed chain. First drive assembly 14 and second drive assembly 16 are onopposite sides of axis A. Motors 52 and 72 of first and second driveassemblies 14 and 16 respectively are spaced generally the same distancefrom axis A. This configuration provides a concentric driving force toramp 20 in the automatic mode to prevent ramp 20 from becomingmisaligned or otherwise twisted in frame 12 as it moves between thestowed and deployed positions. Similarly, in the manual mode, whencontrol assembly 100 is disengaged, linking member 90 rotates aboutdouble sprockets 56 and 76, and thereby coordinates the movement offirst drive chain 50 with that of second drive chain 70. Linking member90 ensures that ramp 20 will thus move an equal distance via each drivechain 50 and 70 during manual stowing and deployment of ramp 12.Furthermore, it is contemplated that if one of the drive motors 52 and72 were to become inoperable, its respective drive gear could bedesigned to freewheel along the fixed chain while the operable motordeploys and stows ramp 20. This provides access system 10 with aredundant system for automatically driving the ramp between its stowedand deployed positions.

[0052] With reference to FIGS. 11-17 there will be described anotheraspect of the invention directed to a wheelchair ramp having sidebarriers. While the side barriers are described with reference to avehicular access system like that of FIGS. 1-10, it should be understoodthat the principles associated with the side barriers of the presentinvention have application with other types of vehicular access systemsfor wheelchairs, including ramps and lifts. In FIGS. 11-17 there isillustrated vehicular access system 210 that, except as described below,is identical to vehicle access system 10 described above. As such,elements in FIGS. 11-17 identical to a corresponding element in FIGS.1-10 are designated with the same reference numeral.

[0053] Referring now to FIGS. 11-14, access system 210 includes a ramp220 extending between an inboard end 220 a and an outboard end 220 b. Afirst side barrier 280 extends along a first lateral edge or side oframp 220 and a second side barrier 290 extends along a second lateraledge or side of ramp 220. Side barrier 280 has an inboard end 280 aco-extensive with inboard end 220 a of ramp 220 and an opposite outboardend 280 b co-extensive with outboard end 220 b of ramp 220. Similarly,side barrier 290 has an inboard end 290 a co-extensive with inboard end220 a of ramp 220 and an opposite outboard end 290 b co-extensive withoutboard end 220 b of ramp 220.

[0054] In FIG. 11 ramp 220 is in its stowed position within side rails24, 26 of frame 12 and side barriers 280, 290 are in their stowedorientation to form a low profile arrangement that allows the ramp andside barriers to fit in frame 12 beneath the floor of the vehicle. It iscontemplated that side barriers 280, 290 are pivotally coupled alongtheir respective lateral edge of ramp 220 with a spring hinge thatbiases the side barriers to their stowed orientation.

[0055] In FIG. 12 ramp 220 is partially deployed from vehicle V, andfirst side barrier 280 and second side barrier (not shown) remain intheir stowed orientation as ramp 220 is extended from frame 12. In FIG.13, ramp 220 is in a deployed position extending from vehicle V and sidebarriers 280, 290 remain in or substantially in their stowedorientations. In FIG. 14, inboard end 220 a of ramp 220 is raised tofloor level F of vehicle V by rocker assembly 32 as discussed above. Asdescribed further below, actuators coupled to rocker assembly 32 contactrespective ones of the side barriers 280, 290 as inboard end 220 a israised to the floor level position, pivoting side barriers 280, 290 totheir raised safety barrier orientation with respect to ramp 220 asshown in FIG. 14. When inboard end 220 a is lowered with rocker assembly32, side barriers 280, 290 are spring biased to return toward theirstowed orientation shown in FIGS. 11, 12 and 13.

[0056] Referring now to FIGS. 15 and 16, there is shown partialperspective views of rocker assembly 32 and a portion of ramp 220connected therewith. Ramp 220 is shown in outline form in hidden linesso as to not obstruct the view of rocker assembly 32. In FIG. 15, rockerassembly 32 and ramp 220 are oriented with respect to one another suchthat inboard end 220 a of ramp 220 is not raised to floor level F; i.e.ramp 220 is in the positions of FIGS. 11, 12 or 13 and rocker assembly32 is generally horizontally oriented. Rocker assembly 32 and ramp 220are rotated in the direction of arrows R to arrive at the ramp/rockerassembly orientation of FIG. 16, wherein inboard end 220 a is raised tofloor level F and rocker assembly 32 is generally vertically oriented,as shown in FIG. 13.

[0057] Second rocker shaft 34 b has a first actuator 250 fixedly coupledthereto and extending laterally from one end thereof, and a secondactuator 260 fixedly coupled to and extending laterally the other endthereof. First actuator 250 and second actuator 260 move along withsecond rocker shaft 34 b as it is raised from its position of FIG. 15 toits position of FIG. 16 by lifting mechanism 37. As such, actuators 250,260 extend generally parallel to or in generally the same plane asrocker assembly 32 when ramp 220 is in its non-raised position of FIG.15. When ramp 220 is raised to its FIG. 16 position, actuators 250, 260follow the rotational movement of second rocker shaft 34 b about firstrocker shaft 34 a and are thus oriented transversely to ramp 220 in agenerally vertical orientation.

[0058] In FIG. 15, first side barrier 280 is in its stowed orientationand pivoted alongside the upper surface of platform 220 over firstactuator 250 (not shown.) Second side barrier 290 is removed so secondactuator 260 can be shown in its stowed orientation. Ramp 220 includes arecess or cutout 224 in a comer thereof extending partially orcompletely through ramp 220. Cutout 224 is sized to receive secondactuator 260 therein so that second actuator 260 is recess below theupper surface of ramp 220 when in its stowed orientation. Similarly,first actuator 250 is positioned in cutout 222 of ramp 220 when in itsstowed orientation. With actuators 250, 260 recessed at or below theupper surface of ramp 220, side barriers 280, 290 can be positionedadjacent to or in contact with the upper surface of ramp 220. Thus, ramp220 and side barriers 280, 290 can assume a lower profile for stowage inframe 12 than would be possible if actuators 250, 260 were locatedbetween side barriers 280, 290 and ramp 220 when side barriers 280, 290were in their stowed orientation.

[0059] In FIG. 16, rocker assembly 32 is rotatled by lift mechanism 37to raise inboard end 220 a of ramp 220 to the vehicle floor level.Actuators 250, 260 are rotated along with second rocker shaft 34 b fromtheir stowed orientation in cutouts 222, 224 and into contact with theadjacent side barrier 280, 290. As actuators 250, 260 are rotated totheir vertical orientation, side barriers 280, 290 are pivoted abouttheir hinged connection with the sides of ramp 220 from their stowedorientation to a raised safety barrier orientation in which sidebarriers 280, 290 are generally vertically and transversely orientedwith respect to ramp 220, as shown by side barrier 280. It iscontemplated that each actuator 250, 260 remains in contact with itsadjacent side barrier 280, 290 to maintain it in the raised safetybarrier orientation and resist its normally spring-bias return towardits stowed orientation. A number of hinged connections 270 along eachside barrier are contemplated. Other mechanisms for pivotally connectingthe side barriers to the sides of ramp 220 are also contemplated aswould occur to those skilled in the art.

[0060] Referring now to FIGS. 17a -17 d, actuators 250, 260 will befurther described with reference to actuator 260, it being understoodthat actuator 250 is mirror image of actuator 260. Actuator 260 includesa first contact portion 262 located towards the center of ramp 220, anda second contact portion 264. Second contact portion 264 is locatedadjacent the pivotal connection between side barrier 290 and ramp 220.Side barrier 290 has a height L1 above ramp 220. In the illustratedembodiment, second contact portion 264 has a height above ramp 220 thatis substantially the same as side barrier 290.

[0061] First contact portion 262 has a height L2 above ramp 220 that isgreater than height L1. This allows first contact portion 262 to contactside barrier 290 before second contact portion 264 when actuator 260 isrotated with second rocker shaft 34 b. Further, by offsetting firstcontact portion 262 toward the center of ramp 220, first contact portion262 contacts side barrier 290 at a location spaced from its pivotalconnection with ramp 220, thus creating a greater moment about thepivotal connection between side barrier 290 and ramp 220 than doessecond contact portion 264.

[0062] As shown in FIG. 17a, actuator 260 is recessed below the uppersurface of ramp 220. In FIG. 17b, ramp 22 has been moved to its deployedposition and can extend downwardly to the ground at an angle relative torocker assembly 32. The pivoting of ramp 220 relative to rocker assembly32 brings first contact portion 262 into contact with side barrier 290,but side barrier 290 is not pivoted sufficiently to interfere withmovement of ramp 220 into and out of frame 12. The length andpositioning of first contact portion 262, as discussed above, generatessufficient force to overcome the spring bias of side barrier 290 towardits stowed orientation and to initiate pivoting movement of side barrier290 toward its raised safety barrier orientation.

[0063] In FIG. 17c, rocker assembly 32 is being pivoted from, itshorizontal orientation toward its vertical orientation to raise theinboard end of ramp 22 to the vehicle floor level. Side barrier 290 hasbeen further pivoted toward its raised safety barrier orientation byactuator 260, and first contact portion 262 is no longer in contacttherewith. Pivoting movement of side barrier 290 is further effectedonly by second contact portion 264, which thereafter remains in contactwith side barrier 290 to maintain it in its raised safety barrierorientation, as shown in FIG. 17d. Actuators 250, 260 are preferablysmooth and rounded to facilitate the sliding movement of the sidebarriers therealong.

[0064] Further shown in FIG. 17d, side barrier 290 has an overlapportion 292 that extends alongside ramp 220. This overlap 292 has alength L3 that corresponds to the thickness of ramp 220, and it iscontemplated that overlap 292 can be in abutting contact with ramp 220when side barrier 290 is in its raised safety barrier orientation. If aforce indicated by arrow F1 were to contact side barrier 290, contactbetween overlap 292 and ramp 220 would assist the hinges or otherpivotal connectors coupling side barrier 290 to ramp 220 in resistingcounterclockwise rotation of side barrier 290. It should be understoodthat side barrier 280 can be similarly configured.

[0065] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same are to be consideredas illustrative and not restrictive in character. It should beunderstood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention are desired to be protected.

What is claimed is:
 1. A vehicle access system, comprising: a frameincluding opposite first and second sides extending between an inboardend and an outboard end; a transfer member movably supported by theframe, the transfer member having an inboard end and an oppositeoutboard end; a first drive assembly positioned adjacent the first sideof the frame; a second drive assembly positioned adjacent the secondside of the frame; a linking member extending between and connecting thefirst drive assembly and the second drive assembly; and a controlassembly engageable to at least one of the linking member, the firstdrive assembly and the second drive assembly, wherein the first driveassembly and the second drive assembly are operable simultaneously tomove the transfer member with respect to the frame between a stowedposition whereby the transfer member is positioned substantially in theframe and a deployed position whereby the transfer member extendsoutwardly from the frame.
 2. The system of claim 1, wherein the transfermember is manually movable between the deployed and stowed positionswhen the control assembly is disengaged from the one of the linkingmember, the first drive assembly and the second drive assembly.
 3. Thesystem of claim 1, wherein: the first drive assembly includes a firstchain mounted to the frame and a first motor coupled to the first chain,the first chain being fixed and the first motor being movable along thefirst chain when the control member is engaged; and the second driveassembly includes a second chain mounted to the frame and a second motorcoupled to the second chain, the second chain being fixed and the secondmotor being movable along the second chain when the control member isengaged.
 4. The system of claim 3, wherein the linking member includes achain extending between and connecting the first drive assembly and thesecond drive assembly.
 5. The system of claim 4, further comprising; afirst double sprocket connecting the first chain of the first driveassembly and the chain of the linking member; and a second doublesprocket connecting the second chain of the second drive assembly andthe chain of the linking member.
 6. The system of claim 5, wherein thecontrol assembly includes a locking member selectively engageable to onethe first and second double sprockets.
 7. The system of claim 1,wherein: the first drive assembly includes a first outboard sprocket, afirst inboard sprocket, and a first double sprocket; and the seconddrive assembly includes a second outboard sprocket, a second inboardsprocket, a reversing sprocket, and a second double sprocket between thesecond inboard sprocket and the reversing sprocket; and the linkingmember is connected to the first double sprocket and the second doublesprocket.
 8. The system of claim 1, wherein the linking member includesa chain extending between and connecting the first drive assembly andthe second drive assembly.
 9. The system of claim 1, further comprisinga carriage attached to the inboard end of the transfer member andmovable in the frame therewith, wherein the first drive assemblyincludes a first motor and the second drive assembly includes a secondmotor, the first motor and the second motor mounted in the carriage. 10.The system of claim 9, wherein: the first drive assembly includes afirst horizontal chain loop mounted to the frame with the first motorcoupled thereto, the first horizontal chain loop being fixed and thefirst motor being movable along the first horizontal chain loop when thecontrol member is engaged; and the second drive assembly includes asecond horizontal chain loop mounted to the frame with the second motorcoupled thereto, the second horizontal chain loop being fixed and thesecond motor being movable along the second horizontal chain loop whenthe control member is engaged.
 11. The system of claim 1, furthercomprising means for raising the inboard end of the transfer member whenthe transfer member is in the deployed position.
 12. The system of claim11, further comprising a carriage movable in the frame and attached tothe inboard end of the transfer member, wherein the means for raisingincludes a rocker assembly pivotally attached to and extending betweenan outboard end of the carriage and the inboard end of the transfermember.
 13. A vehicle access system, comprising: a frame includingopposite first and second sides extending between an inboard end and anoutboard end; a transfer member movably mounted to the frame, thetransfer member having an inboard end and an opposite outboard end; afirst drive assembly positioned along the first side of the frame, thefirst drive assembly including a first chain and a first motor coupledto the first chain; a second drive assembly positioned along the secondside of the frame, the second drive assembly including a second chainand a second motor coupled to the second chain; and a linking memberconnected between the first drive assembly and the second driveassembly, wherein the first drive assembly and the second drive assemblyare operable simultaneously to move the transfer member with respect tothe frame between a stowed position whereby the transfer member ispositioned substantially in the frame and an deployed position wherebythe transfer member extends outwardly from the frame.
 14. The system ofclaim 13, further comprising a control assembly selectively engageableto one of the linking member, the first drive assembly and the seconddrive assembly.
 15. The system of claim 14, wherein the transfer memberis manually movable between the deployed position and the stowedposition when the control assembly is not selectively engaged to the oneof the linking member, the first drive assembly and the second driveassembly.
 16. The system of claim 14, wherein the first motor is movablealong the first chain and the second motor is movable along the secondchain to move the transfer member between the deployed and stowedpositions when the control member is selectively engaged to the one ofthe linking member, the first drive assembly and the second driveassembly.
 17. The system of claim 13, wherein the first chain forms afirst loop and the second chain forms a second loop, the first loop andthe second loop being oriented parallel to the transfer member.
 18. Thesystem of claim 13, wherein the linking member includes a chainextending along the inboard end of the frame and connecting the firstdrive assembly and the second drive assembly.
 19. A vehicle accesssystem, comprising: a frame mounted to the vehicle, the frame includingopposite first and second sides extending between an inboard end and anoutboard end; a transfer member movably mounted to the frame, thetransfer member having an inboard end and an opposite outboard end; afirst drive assembly positioned towards the first side of the frame; asecond drive assembly positioned towards the second side of the frame;and a linking member extending along the inboard end of the frame andconnecting the first drive assembly and the second drive assembly tomaintain the first and second drive assemblies simultaneously in one ofa manual mode or an automatic mode.
 20. The system of claim 19, whereinwhen in the automatic mode the transfer member is movable with respectto the frame by the first and second drive assemblies between a stowedposition whereby the transfer member is positioned substantially in thevehicle and a deployed position whereby the transfer member extendsoutwardly from the vehicle.
 21. The system of claim 19, wherein thetransfer member has a central axis extending between the inboard end andthe outboard end of the transfer member and the first drive assembly andthe second drive assembly are each spaced a substantially equal distancefrom the central axis.
 22. The system of claim 19, further comprising acontrol assembly selectively engageable to one of the first driveassembly, the second drive assembly and the chain, wherein: the firstdrive assembly includes a first drive chain mounted to the frame and afirst motor coupled to the first drive chain, the first drive chainbeing fixed and the first motor being movable along the first drivechain when the control assembly is engaged to one of the first driveassembly, the second drive assembly and the chain; and the second driveassembly includes a second drive chain mounted to the frame and a secondmotor coupled to the second drive chain, the second drive chain beingfixed and the second motor being movable along the second chain drivewhen the control assembly is engaged to the one of the first driveassembly, the second drive assembly and the chain.
 23. The system ofclaim 22, further comprising; a first double sprocket connecting thefirst drive chain and the linking member; and a second double sprocketconnecting the second drive chain and the linking member.
 24. A vehicleaccess system, comprising: a frame; a first drive assembly attached tothe transfer member and attached to the frame, the first drive assemblycomprising: a first chain forming a first substantially horizontal loopabout a first plurality of sprockets; and a first motor engaging aportion of the first chain; a second drive assembly attached to thetransfer member and attached to the frame, the second drive assemblycomprising: a second chain forming a second substantially horizontalloop about a second plurality of sprockets; and a second motor engaginga portion of the second chain; a linking member interconnecting thefirst drive assembly and the second drive assembly; and a controlassembly selectively engageable to one of the first drive assembly, thesecond drive assembly and the linking member, wherein the first driveassembly and the drive assembly are operable simultaneously to move thetransfer member with respect to the frame between a stowed positionwhereby the transfer member is positioned substantially in the frame anda deployed position whereby the transfer member extends outwardly fromthe frame.
 25. The system of claim 24, wherein: the first motor movesalong the first chain to move the transfer member when the controlassembly is engaged; and the second motor moves along the second chainto move the transfer member when the control assembly is engaged. 26.The system of claim 24, wherein the first chain rotates about the firstplurality of sprockets and the second chain rotates about the secondplurality of sprockets for manual movement of the transfer memberbetween the stowed position and the deployed position when the controlassembly is disengaged.
 27. The system of claim 24, wherein the linkingmember is a third chain forming a third substantially horizontal loopconnected with one of the first plurality of sprockets and one of thesecond plurality of sprockets at an inboard end of the frame.